Method for polymerising ethylene

ABSTRACT

The invention concerns a method for producing ethylene homopolymers or copolymers comprising at least 90 mol % of units derived from ethylene which consists in: contacting in polymerising conditions, the monomers with a catalytic system including: (a) a catalytic solid comprising a metallocene of a transition metal of groups 4 to 6 of the periodic table containing at least a cyclopentadiene ligand capable of being substituted and a support, (b) at least an organoaluminium compound selected among compounds of general formula (1): AIT x (Y′) y X′ z  wherein: T is a hydrocarbon group containing 1 to 30 carbon atoms; Y′ is a group selected among —OR′, —SR′ and NR′R″ with R′ and R″ independently representing a hydrocarbon group containing 1 to 30 carbon atoms; X′ is a halogen atom: x verifies the relationship 0&lt;x≦3; y verifies the relationship 0≦y&lt;3; z verifies the relationship 0≦z&lt;3, and x+y+z=3, and (c) at least an ionic antistatic agent.

[0001] The present invention relates to a process for polymerizingethylene.

[0002] It is known to polymerize ethylene by means of metallocenecatalysts. Such processes result in the manufacture of polyethyleneshaving a low bulk density (BD).

[0003] Moreover, the use of antistatic agents in industrialpolymerization processes is well known. These antistatic agents reduceelectrical charges and thus prevent the formation of agglomerates and ofdeposits on the walls of the polymerization reactors. Patentapplications WO 99/61486 and WO 96/11960 disclose processes forpolymerizing ethylene using a supported metallocene, an aluminoxane, atrialkylaluminum and a nonionic antistatic agent chosen fromdiethoxylated tertiary alkylamines, which do not cause coating. Patentapplication EP 0 803 514 discloses a process for (co)polymerizingpropylene using a supported metallocene catalyst, an aluminoxane, atrialkylaluminum and an ionic antistatic agent, which does not causecoating nor the formation of agglomerates.

[0004] A process has now been discovered for polymerizing ethylene whichmakes it possible to obtain polyethylenes of high bulk density with ahigh catalytic activity and without the walls of the reactor beingfouled.

[0005] For this purpose, the present invention relates to a process formanufacturing ethylene homopolymers or ethylene copolymers comprising atleast 90 mol % of units derived from ethylene, in which processethylene, and optionally the other monomers, are brought into contact,under polymerizing conditions, with a catalytic system comprising:

[0006] (a) a catalytic solid comprising a metallocene of a transitionmetal of Groups 4 to 6 of the Periodic Table, which contains at leastone cyclopentadiene ligand, possibly substituted, deposited on asupport;

[0007] (b) at least one organoaluminum compound chosen from compoundssatisfying the general formula (1)

AlT_(x)(Y′)_(y)X′_(z)   (1)

[0008] in which:

[0009] T is a hydrocarbon group containing from 1 to 30 carbon atoms,

[0010] Y′ is a group chosen from —OR′, —SR′ and NR′R″, where R′ and R″represent, independently, a hydrocarbon group containing from 1 to 30carbon atoms,

[0011] X′ is a halogen atom,

[0012] x is a number satisfying the condition

[0013] 0<x≦3,

[0014] y is a number satisfying the condition 0≦y<3,

[0015] z is a number satisfying the conditions 0≦z<3 and x+y+z=3; and

[0016] (c) at least one ionic antistatic agent.

[0017] According to the present invention, the expression “process forpolymerizing ethylene” is understood to mean a process for manufacturingethylene homopolymers and ethylene copolymers comprising at least 90 mol% of units derived from ethylene. The preferred copolymers are those ofethylene with another alpha-olefin comprising from 3 to 8 carbon atoms.Particularly preferred are ethylene/1-butene and/or ethylene/1-hexenecopolymers.

[0018] The metallocene used in the process according to the presentinvention is usually chosen from compounds satisfying the formula

Q_(a) (C₅H_(5-a-b)R¹ _(b)) (C₅H_(5-a-c)R² _(c)) MeXY   (2)

[0019] in which:

[0020] Q represents a divalent linking group between the twocyclopentadiene ligands (C₅H_(5-a-b)R¹ _(b))) and (C₅H_(5-a-c)R² _(c)) ;

[0021] a equals 0 or 1;

[0022] b, c and d are integers satisfying the conditions 0≦b≦5, 0≦c≦5and 0≦d≦5 when a equals 0, and 0≦b≦4, 0≦c≦4 and 0≦d≦4 when a equals 1;

[0023] R¹ and R² each represent hydrocarbon groups containing from 1 to20 carbon atoms and able to be linked to the cyclopentadiene ring in theform of a monovalent group or able to be connected to each other so asto form a ring adjacent to the cyclopentadiene ring, halogen atoms,alkoxy groups having from 1 to 12 carbon atoms, silicon-containinghydrocarbon groups of formula —Si(R⁴)(R⁵) (R⁶), phosphorus-containinghydrocarbon groups of formula —P(R⁴) (R⁵), nitrogen-containinghydrocarbon groups of formula —N(R⁴)(R⁵) or boron-containing hydrocarbongroups of formula —B(R⁴)(R⁵) in which R⁴, R⁵ and R⁶ representhydrocarbon groups containing from 1 to 24 carbon atoms, as long as whenb, c or d equals 2 or more and/or a plurality of groups R¹ or R² exist,the latter may be identical or different;

[0024] Me represents a transition metal of Groups 4 to 6 of the PeriodicTable; and

[0025] X and Y, which are identical or different, each represent ahydrogen atom, a halogen atom, a hydrocarbon group, an alkoxy group, anamino group, a phosphorus-containing hydrocarbon group or asilicon-containing hydrocarbon group having from 1 to 20 carbon atoms.

[0026] The preferred transition metal compounds of formula (2) aregenerally such that:

[0027] Q represents an alkylene group containing 1 or 2 carbon atoms,possibly substituted with alkyl or aryl groups containing from 1 to 10carbon atoms, or a dialkylgermanium or dialkylsilicon group containingfrom 1 to 6 carbon atoms;

[0028] a equals 0 or 1;

[0029] b, c and d are integers satisfying the conditions 0≦b≦5, 0≦c≦5and 0≦d≦5 when a equals 0, and 0≦b≦4, 0≦c≦4 and 0≦d≦4 when a equals 1;

[0030] R¹ and R² represent alkyl, alkenyl, aryl, alkylaryl, alkenylarylor arylalkyl groups containing from 1 to 20 carbon atoms, it beingpossible for several groups R¹ and/or several groups R² to be linked toeach other so as to form a ring containing from 4 to 8 carbon atoms;

[0031] Me is zirconium, hafnium or titanium; and

[0032] X and Y represent halogen atoms or hydrocarbon groups chosen fromalkyls, aryls and alkenyls containing from 1 to 10 carbon atoms.

[0033] Particularly preferred are metallocenes of formula (2) in which Qis a linking group chosen from dimethylsilyl and diphenylsilyl, ethyleneand methylenes and ethylenes substituted with alkyl or aryl groupscontaining from 1 to 8 carbon atoms. Particularly suitable compounds offormula (2) are compounds in which the ligands (C₅H_(5-a-b)R¹ _(b)) and(C₅H_(5-a-c)R² _(c)) are chosen from cyclopentadienyls, indenyls andfluorenyls, these possibly being substituted. The catalytic solid (a)usually also includes an activator. The activator is generally chosenfrom aluminoxanes and ionizing agents.

[0034] The term “aluminoxanes” is understood to mean compoundssatisfying the formula R⁷—(AlR⁷—O)_(m)-AlR⁷ ₂ and the cyclic compoundssatisfying the formula (—AlR⁷—O—)_(m+2) in which m is a number from 1 to40 and R⁷ is an alkyl or aryl group containing from 1 to 12 carbonatoms. The preferred compounds are chosen from methyaluminoxanes,ethylaluminoxanes, isobutylaluminoxanes and mixtures thereof, and moreparticularly those in which m is a number from 2 to 20. Mostparticularly preferred is methylaluminoxane (MAO) in which m is a numberfrom 10 to 18.

[0035] The term “ionizing agents” is understood to mean compoundscomprising a first part which has the properties of a Lewis acid and iscapable of ionizing the metallocene and a second part which is inertwith respect to the ionized metallocene and is capable of stabilizingit. As examples of such compounds, mention may be made oftriphenylcarbenium tetrakis(pentafluorophenyl)borate,N,N-dimethylanilium tetrakis(pentafluorophenyl)borate,tri(n-butyl)ammonium tetrakis(pentafluorophenyl)borate,tri(pentafluorophenyl)boron, triphenylboron, trimethylboron,tri(trimethylsilyl)boron and organoboroxines.

[0036] The amount of activator in the catalytic solid depends on thetype of activator used. When the activator is an aluminoxane, the amountof aluminoxane is usually such that the atomic ratio of aluminum comingfrom the aluminoxane to the transition metal coming from the metalloceneis from 2 to 5000. Preferably, this ratio is at least 5, moreparticularly at least 10. Good results are obtained when this ratio isat least 20. Usually the aluminoxane is employed in amounts such thatthe aluminum/transition metal atomic ratio is at most 2000, moreparticular at most 1500. Atomic ratios of aluminum coming from thealuminoxane of [sic] the transition metal of at most 1000 are mostparticularly preferred. Ratios of at most 300 give good results. Whenthe activator is an ionizing agent, the amount of ionizing agent isusually such that the molar ratio of the ionizing agent to themetallocene is from 0.05 to 50. Preferably, this ratio is at least 0.1and more particularly at most 20.

[0037] The catalytic solid (a) contains a support. The support may beany known organic or inorganic support allowing the metallocene andpossibly the activator to be supported. As nonlimiting examples ofinorganic supports, mention may be made of talc or inorganic oxides-suchas silicas, aluminas, titanium, zirconium or magnesium oxides, ormixtures thereof. Such supports have been disclosed in patentapplication EP 0 206 794 for example. The organic supports are usuallychosen from among porous polymeric supports, and more particularly fromamong polyolefin supports such as those disclosed in patent applicationEP 1 038 883. Inorganic supports are preferred within the context of thepresent invention. Silica is particularly preferred.

[0038] The catalytic solid (a) used in the process according to theinvention may be obtained by various methods. In general, supportparticles are brought into contact with a solution containing theactivator in order to obtain a suspension which is then evaporated. Themetallocene may be introduced into the suspension described above. Itmay also have been incorporated into the support before it is broughtinto contact with the activator. Finally, it may be brought into contactwith the support particles containing the activator.

[0039] The catalytic solid (a) employed in the process according to thepresent invention generally contains from 0.001 to 5 g of metalloceneper gram of support. Preferably, the concentration of metallocene is atleast 0.005 g and more particularly at least 0.01 g per gram of support.Amounts of metallocene less than or equal to 3 and preferably less thanor equal to 1 g per gram of support give good results.

[0040] According to a variant of the process according to the invention,a catalytic solid (a) is used that has been subjected to a preliminarypolymerization during which it is brought into contact with analpha-olefin, under polymerizing conditions, so as to form from 0.01 to50 g of polyolefin per g of catalytic solid. The alpha-olefin usedduring the preliminary polymerization step is advantageously chosen fromamong alpha-olefins containing from 2 to 4 carbon atoms.

[0041] The catalytic system also includes at least one organoaluminumcompound (b) satisfying the general formula (1). The organoaluminumcompound is preferably chosen from among trialkylaluminums of formulaAlT₃, and more particularly from among those in which each T represents,independently, an alkyl group containing from 1 to 20 carbon atoms.Particularly preferred is a trialkylaluminum in which T is an alkylgroup containing from 1 to 6 carbon atoms, such as trimethylaluminum(TMA), triethylaluminum and triisobutylaluminum (TIBAL).

[0042] The amount of organoaluminum compound (b) employed in the processaccording to the invention is in general such that the atomic ratio ofthe aluminum coming from the organoaluminum compound (b) to thetransition metal coming from the metallocene is from 10 to 50 000.Preferably, this ratio is at least 20, more particularly at least 30.Goods results are obtained when this ratio is at least 40. Usually theorganoaluminum compound (b) is employed in amounts such that thealuminum coming from the organoaluminum compound/transition metal comingfrom the metallocene atomic ratio is at most 20 000 and moreparticularly at most 17 000. Ratios of at most 15 000 give good results.

[0043] The catalytic system used in the process according to theinvention also includes at least one ionic antistatic agent (c). Withinthe context of the present invention, the ionic antistatic agents aregenerally chosen from among those containing a long hydrophobic chain.Preferably, ionic antistatic agents comprising at least one hydrocarbongroup containing from 6 to 35 carbon atoms is used, this group beingpossibly substituted.

[0044] According to a first variant of the process according to theinvention, the antistatic agent is chosen from among cationic antistaticagents and more particularly from among quaternary ammonium saltsrepresented by the general formula A¹A²A³A⁴NX¹ in which A¹, A², A³ andA⁴ represent, independently, a hydrocarbon group containing from 1 to 35carbon atoms and at least one of A¹, A², A³ and A⁴ is a hydrocarbongroup containing from 6 to 35 carbon atoms, and X¹ is a halogen atom.Quaternary alkylammonium salts containing at least one alkyl groupcontaining from 6 to 35 carbon atoms are preferred. Quaternaryalkylammonium salts containing at least one alkyl group containing from6 to 35 carbon atoms derived from a fatty acid give good results. As anonlimiting example of a quaternary ammonium salt, mention may be madeof dicocoalkyldimethylammonium chloride. The product commerciallyavailable under the name CHEMAX® X-997 is particularly preferred.

[0045] According to a second variant of the process, the antistaticagent is chosen from among anionic antistatic agents and moreparticularly from among sulfonic acids comprising at least onehydrocarbon group containing from 6 to 35 carbon atoms, this grouppossibly being substituted. Sulfonic acids comprising a hydrocarbongroup, preferably an aryl group, containing from 6 to 18 carbon atomsand substituted with at least one alkyl group containing from 6 to 16carbon atoms give good results. As a nonlimiting example of a sulfonicacid, mention may be made of dinonylnaphthalenesulfonic acid. Theproduct sold by the company Octel under the name STADIS® 450 isparticularly preferred.

[0046] The amount of antistatic agent employed in the process accordingto the invention is in general such that the molar ratio of theantistatic agent (c) to the organoaluminum compound (b) is less than0.5. Preferably, the molar ratio of the antistatic agent to theorganoaluminum compound is less than 0.2. Molar ratios of less than 0.1are particularly preferred. The amount of antistatic agent is such thatthe molar ratio of the antistatic agent (c) to the organoaluminumcompound (b) is in general at least 0.001. Preferably, this molar ratiois at least 0.002, more particularly at least 0.003.

[0047] In the process according to the invention, it is advantageous toprepare a premixture comprising at least the organoaluminum compound (b)and the antistatic agent (c), before the catalytic solid (a) is addedthereto.

[0048] The polymerization process according to the invention may becarried out continuously or batchwise, by whatever known process. Thepolymerization process is preferably carried out in suspension in ahydrocarbon diluent. The hydrocarbon diluent is generally chosen fromamong aliphatic hydrocarbons containing from 3 to 10 carbon atoms.Preferably, the diluent is chosen from among propane, isobutane, hexaneor mixtures thereof.

[0049] The temperature at which the polymerization process according tothe invention is carried out is generally from −20° C. to +150° C.,usually from 20 to 130° C. The polymerization temperature is preferablyat least 60° C. Preferably, it does not exceed 115° C.

[0050] The total pressure at which the process according to theinvention is carried out is in general chosen to be between atmosphericpressure and 100×10⁵ Pa, more particularly between 10×10⁵ and 55×10⁵ Pa.

[0051] The molecular mass of the polymers manufactured according to theprocess of the invention may be controlled by addition of one or moreagents for controlling the molecular mass of polyolefins, such as moreparticularly hydrogen.

[0052] In a variant of the process according to the invention, theprocess comprises a first polymerization step, separate from thepreliminary polymerization step (described above in relation to thecatalytic solid) and called prepolymerization step, during which from 1to 1000 g of polymer per g of catalytic solid are formed. The amount ofprepolymer formed in this prepolymerization step is advantageously atleast 3 g per g of catalytic solid. Good results are obtained when theamount of prepolymer is at most 700 g per g of catalytic solid. Ingeneral, the prepolymerization step is carried out at a temperature from0 to 60° C.

[0053] The process according to the invention makes it possible toobtain catalytic activities considerably higher than in the process withno ionic antistatic agent, without the walls of the reactor beingfouled, while at the same time giving polyethylenes having a higher bulkdensity (BD). Obtaining polymers having high BDs has the advantage ofincreasing the production capability of polymerization plants and ofincreasing storage and transport capabilities.

[0054] The following examples serve to illustrate the invention. Themethods for measuring the parameters mentioned in the examples and theunits expressing these parameters will be explained below.

[0055] The catalytic activity is characterized by the amount ofpolyethylene formed during polymerization trials and is expressed in kgof polyethylene per mmol of transition metal coming from the metalloceneemployed, per hour of polymerization and per 10⁵ Pa. In examples 10 to13R, the catalytic activity is assessed indirectly from thedetermination by gas chromatography of the residual ethylene in the gasleaving the reactor.

[0056] The BD of the polyethylene obtained is expressed in kg/m³. The BDof the polyethylene is measured under free flow using the followingoperating method: the polyethylene coming from the polymerizationprocess is poured into a cylindrical container of 50 cm³ capacity,taking care not to compact it, from a hopper whose lower edge is placed20 mm above the upper edge of the container. The container filled withthe powder is then weighed, the tare is deducted from the recordedweight and the result obtained, expressed in kg, is multiplied by 20 000so as to express the BD in kg/m³.

[0057] In examples 1 to 9R, the concentration of antistatic agent isexpressed in ppm with respect to isobutane.

EXAMPLES 1 AND 2

[0058] 1.8 mmol of TIBAL, the antistatic agent(dicocoalkyldimethylammonium chloride sold under the name CHEMAX® X-997or dinonylnaphthalenesulfonic acid sold under the name STADIS® 450 byOctel) (dissolved in hexane) and 1800 ml of isobutane were introduced,with dry nitrogen purging, into a dry 5-liter autoclave fitted with astirrer.

[0059] The temperature was increased up to 80° C. and ethylene was addedso as to obtain an ethylene partial pressure of 10×10⁵ Pa.

[0060] The polymerization was started by sending the catalytic solid,comprising 6% by weight ofethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride and 47.5%by weight of MAO (corresponding to 22.1% by weight of aluminum), onto asilica support with 200 ml of isobutane.

[0061] The temperature and the ethylene partial pressure were keptconstant throughout the duration of polymerization (1 hour). Thereaction was stopped by degassing and cooling the reactor. Thepolyethylene was recovered by draining the reactor and was dried.

[0062] The polymerization conditions and the results obtained are givenin table 1. In no case was coating of the reactor observed. TABLE 1Catalytic solid Antistatic agent Ex. (mg) Type ppm Activity BD 1 63Chemax ® X-997 20 44 342 2 63 Stadis ® 450 20 46 352 3R 66 — — 39 229

EXAMPLE 3R (NOT ACCORDING TO THE INVENTION)

[0063] The operations of example 1 were repeated, but without addingantistatic agent. The results obtained are also given in table 1.

[0064] This shows that the addition of an ionic antistatic agent makesit possible to obtain, with a better yield, polyethylenes having ahigher BD.

EXAMPLES 4 TO 8

[0065] 0.9 mmol of TIBAL and 800 ml of isobutane were introduced, withdry nitrogen purging, into a dry 3-liter autoclave fitted with astirrer.

[0066] The temperature was increased up to 80° C. and hydrogen was addedso as to obtain the desired H₂/ethylene molar ratio in the gas phase.Next, ethylene was introduced until an ethylene partial pressure of10×10⁵ Pa was obtained.

[0067] The antistatic agent (CHEMAX® X-997 or STADIS® 450 from Octel)(dissolved in hexane) was sent to the reactor with 100 ml of isobutane,and the polymerization was started by sending the catalytic solid asdescribed in example 1, with 100 ml of isobutane.

[0068] The temperature, ethylene partial pressure and H₂/ethylene ratiowere kept constant throughout the duration of polymerization (1 hour).The reaction was stopped by cooling and degassing the reactor. Thepolyethylene was recovered by draining the reactor and was dried.

[0069] The polymerization conditions and the results obtained are givenin table 2. In no case was coating of the reactor observed. TABLE 2Catalytic solid H₂/ethylene Antistatic agent Activ- Ex. (mg) (mol/mol)Type ppm ity 4 154 0.0021 Chemax ® X-997 10 20 5 155 0.0020 Chemax ®X-997 20 26 6 152 0.0023 Chemax ® X-997 40 25 7 148 0.0022 Stadis ® 45025 18 8 149 0.0021 Stadis ® 450 50 25 9R 153 0.0023 — — 13

EXAMPLE 9R (NOT ACCORDING TO THE INVENTION)

[0070] The operations of example 6 were repeated, but without addingantistatic agent. The results obtained are given in table 2. Table 2shows that the addition of an antistatic agent makes it possible toincrease the catalytic activity considerably.

EXAMPLE 10

[0071] Isobutane, ethylene, hydrogen, TIBAL, CHEMAX® X-997 and thecatalytic solid, described in example 1, were continuously introducedinto a loop reactor. The polymerization conditions are given in table 3.The suspension comprising the polyethylene was continuously removed fromthe reactor and subjected to reduced pressure so as to evaporate theisobutane, the hydrogen and the ethylene so as to recover thepolyethylene in the form of a powder, which was then dried. The ethylenecontent in the gas leaving the reactor was 12.2 mol %.

[0072] After 15 days of continuous polymerization, the reactor wasstopped and inspected. The reactor was free of coating. TABLE 3 Ex. 10Ex. 11R Ex. 12 Ex. 13R Chemax ® X-997 (g/h) 0.468 0 0 0 Stadis ® 450(g/h) 0 0 0.33 0 TIBAL (g/h) 13.0 13.0 13.5 13.4 H₂/ethylene (% mol/mol)0.03 <0.03 0.06 0.03 Catalytic solid (g/h) 5.6 5.6 10.2 10.2 Temperature(° C.) 80 80 80 80 Residence time (h) 1.25 1.2 1.28 1.31 Outgoingethylene (mol %) 12.2 16.7 7.1 12.6

EXAMPLE 11R

[0073] The operations of example 10 were repeated but without theCHEMAX® X-997 feed, but with the catalyst and hydrogen feed unchanged.The ethylene content in the gas leaving the reactor was 16.7 mol %.

[0074] Comparing example 10 with example 11R demonstrates that theaddition of an antistatic agent makes it possible to obtain a betterconversion of the ethylene (less ethylene in the gas leaving thereactor), hence a higher catalytic efficiency.

EXAMPLE 12

[0075] The operations of example 10 were repeated, but using the STADIS®450 from Octel in an amount of 0.33 g/h instead of the CHEMAX® X-997.The ethylene content in the gas leaving the reactor was 7.1 mol %.

EXAMPLE 13R

[0076] The operations of example 12 were repeated, but without theSTADIS® 450 feed but with the catalyst and hydrogen feed unchanged. Theethylene content in the gas leaving the reactor was 12.6 mol %.

[0077] Comparing example 12 with example 13R demonstrates that theaddition of an antistatic agent makes it possible to obtain a betterconversion of ethylene (less ethylene in the gas leaving the reactor),hence a higher catalytic efficiency.

1. A process for manufacturing ethylene homopolymers or ethylenecopolymers comprising at least 90 mol % of units derived from ethylene,in which process ethylene, and optionally the other monomers, arebrought into contact, under polymerizing conditions, with a catalyticsystem comprising: (a) a catalytic solid comprising a metallocene of atransition metal of Groups 4 to 6 of the Periodic Table, which containsat least one cyclopentadiene ligand, possibly substituted, deposited ona support; (b) at least one organoaluminum compound chosen fromcompounds satisfying the general formula (1) AlT_(x)(Y′)_(y)X′_(z)   (1)in which: T is a hydrocarbon group containing from 1 to 30 carbon atoms,Y′ is a group chosen from —OR′, —SR′ and NR′R″, where R′ and R″represent, independently, a hydrocarbon group containing from 1 to 30carbon atoms, X′ is a halogen atom, x is a number satisfying thecondition 0<x≦3, y is a number satisfying the condition 0≦y<3, z is anumber satisfying the conditions 0≦z<3 and x+y+z=3; and (c) at least oneionic antistatic agent.
 2. The process as claimed in claim 1, in whichthe metallocene is chosen from compounds satisfying the formulaQ_(a)(C₅H_(5-a-b)R¹ _(b)) (C₅H_(5-a-c)) R² _(c))MeXY   (2) in which: Qrepresents a divalent linking group between the two cyclopentadieneligands (C₅H_(5-a-b)R¹ _(b)) and (C₅H_(5-a-c)R² _(c)); a equals 0 or 1;b, c and d are integers satisfying the conditions 0≦b≦5, 0≦c≦5 and 0≦d≦5when a equals 0, and 0≦b≦4, 0≦c≦4 and 0≦d≦4 when a equals 1; R¹ and R²each represent hydrocarbon groups containing from 1 to 20 carbon atomsand able to be linked to the cyclopentadiene ring in the form of amonovalent group or able to be connected to each other so as to form aring adjacent to the cyclopentadiene ring, halogen atoms, alkoxy groupshaving from 1 to 12 carbon atoms, silicon-containing hydrocarbon groupsof formula —Si(R⁴)(R⁵)(R⁶), phosphorus-containing hydrocarbon groups offormula —P(R⁴)(R⁵), nitrogen-containing hydrocarbon groups of formula—N(R⁴)(R⁵) or boron-containing hydrocarbon groups of formula —B(R⁴) (R⁵)in which R⁴, R⁵ and R⁶ represent hydrocarbon groups containing from 1 to24 carbon atoms, as long as when b, c or d equals 2 or more and/or aplurality of groups R¹ or R² exist, the latter may be identical ordifferent; Me represents a transition metal of Groups 4 to 6 of thePeriodic Table; and X and Y, which are identical or different, eachrepresent a hydrogen atom, a halogen atom, a hydrocarbon group, analkoxy group, an amino group, a phosphorus-containing hydrocarbon groupor a silicon-containing hydrocarbon group having from 1 to 20 carbonatoms.
 3. The process as claimed in claim 1 or 2, in which the catalyticsolid (a) furthermore contains an activator, preferably an aluminoxanechosen from among methylaluminoxanes, ethylaluminoxanes,isobutylaluminoxanes and mixtures thereof.
 4. The process as claimed inany one of claims 1 to 3, in which the support is a silica.
 5. Theprocess as claimed in any one of claims 1 to 4, in which theorganoaluminum compound (b) is chosen from among trialkylaluminums offormula AlT₃ in which each T represents an alkyl group comprising from 1to 6 carbon atoms.
 6. The process as claimed in any one of claims 1 to5, in which the ionic antistatic agent (c) is chosen from amongquaternary ammonium salts represented by the general formula A¹A²A³A⁴NX¹in which A¹, A², A³ and A⁴ representing [sic], independently, ahydrocarbon group containing from 1 to 35 carbon atoms and at least oneof A¹, A², A³ and A⁴ is a hydrocarbon group containing from 6 to 35carbon atoms, and X¹ is a halogen atom.
 7. The process as claimed inclaim 6, in which the ionic antistatic agent (c) isdicocoalkyldimethylammonium chloride.
 8. The process as claimed in anyone of claims 1 to 5, in which the ionic antistatic agent (c) is chosenfrom among sulfonic acids comprising at least one hydrocarbon groupcontaining from 6 to 35 carbon atoms, this group possibly beingsubstituted.
 9. The process as claimed in claim 8, in which the ionicantistatic agent (c) is dinonylnaphthalenesulfonic acid.
 10. The processas claimed in any one of claims 1 to 9, in which the molar ratio of theantistatic agent (c) to the organoaluminum compound (b) is less than0.5.